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zhanshuiqing银虫 (小有名气)
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[求助]
SN曳力模型（Schiller &Naumann)udf修正的求助？？？ 已有1人参与
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在计算气液两相流欧拉模型，发现气泡运动过程中发生变形，考虑气泡颗粒尺寸的变化，觉得fluent常用的SN曳力模型不太好，就自编了一个修正的曳力模型udf，可是计算的时候，收敛过程非常不稳定，效果很差，找不到原因，大家给指点下啊 #include "udf.h" #include "sg.h" #include "sg_mphase.h" #include "flow.h" #include "mem.h" #include "metric.h" #define g 9.81 #define surface_t 0.132 /* surface tension coefficient*/ #define diam2 1.e-2 DEFINE_EXCHANGE_PROPERTY(custom_drag,cell,mix_thread,s_col,f_col) { Thread *thread_l, *thread_g; real x_vel_l, x_vel_g, y_vel_l, y_vel_g, z_vel_l, z_vel_g,abs_v, slip_x, slip_y,slip_z, rho_l, rho_g,delta_rho, mu_l, reyp, Eo, C_D1,C_D2,C_D,void_g,void_l, fdrgs, taup, k_g_s; /* find the threads for the liquid (primary phases) and solids (secondary phases)*/ thread_l = THREAD_SUB_THREAD(mix_thread, s_col);/* liquid phase */ thread_g = THREAD_SUB_THREAD(mix_thread, f_col);/* gas phase*/ /* find phase velocities and properties*/ x_vel_l = C_U(cell, thread_l); y_vel_l = C_V(cell, thread_l); z_vel_l = C_W(cell, thread_l); x_vel_g = C_U(cell, thread_g); y_vel_g = C_V(cell, thread_g); z_vel_g = C_W(cell, thread_g); /* slip velocity*/ slip_x = x_vel_l - x_vel_g; slip_y = y_vel_l - y_vel_g; slip_z = z_vel_l - z_vel_g; /*Parameters*/ rho_l = C_R(cell, thread_l); rho_g = C_R(cell, thread_g); delta_rho = rho_l - rho_g; mu_l = C_MU_L(cell, thread_l); /*compute slip*/ abs_v = sqrt(slip_x*slip_x + slip_y*slip_y + slip_z*slip_z); /*compute Reynold's number*/ reyp = rho_l*abs_v*diam2/mu_l; /*compute Eotvos number*/ Eo = g*delta_rho*diam2*diam2/surface_t; /*compute particle relaxtion time*/ taup = rho_g*diam2*diam2/18./mu_l; void_g = C_VOF(cell,thread_g); void_l = 1.-void_g; /*compute C_D */ C_D1 =24.*(1.+0.15*pow(reyp, 0.687))/reyp; C_D2 = 8./3.*Eo/(Eo+4.); if(C_D1 > C_D2) C_D = C_D1; else C_D = C_D2; /*compute drag and return drag coeff, k_g_s*/ fdrgs = C_D*reyp/24.0; k_g_s = void_g*void_l*rho_g*fdrgs/taup; return k_g_s; } |
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jiangfan2008
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2楼2013-05-04 01:15:16
bingyee007
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3楼2013-06-04 20:39:54
【答案】应助回帖
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气泡尺寸给你修改了，你的气泡尺寸太大，3-5mm比较好吧？ #include "udf.h" #include "sg.h" #include "sg_mphase.h" #include "flow.h" #include "mem.h" #include "metric.h" #define g 9.81 #define surface_t 0.073 /* surface tension coefficient*/ #define diam2 4.e-3 DEFINE_EXCHANGE_PROPERTY(custom_drag,cell,mix_thread,s_col,f_col) { Thread *thread_l, *thread_g; real x_vel_l, x_vel_g, y_vel_l, y_vel_g, z_vel_l, z_vel_g,abs_v, slip_x, slip_y,slip_z, rho_l, rho_g,delta_rho, mu_l, reyp, Eo, C_D1,C_D2,C_D,void_g,void_l, fdrgs, taup, k_g_s; /* find the threads for the liquid (primary phases) and gas (secondary phases)*/ thread_l = THREAD_SUB_THREAD(mix_thread, s_col);/* liquid phase */ thread_g = THREAD_SUB_THREAD(mix_thread, f_col);/* gas phase*/ /* find phase velocities and properties*/ x_vel_l = C_U(cell, thread_l); y_vel_l = C_V(cell, thread_l); z_vel_l = C_W(cell, thread_l); x_vel_g = C_U(cell, thread_g); y_vel_g = C_V(cell, thread_g); z_vel_g = C_W(cell, thread_g); /* slip velocity*/ slip_x = x_vel_l - x_vel_g; slip_y = y_vel_l - y_vel_g; slip_z = z_vel_l - z_vel_g; /*Parameters*/ rho_l = C_R(cell, thread_l); rho_g = C_R(cell, thread_g); delta_rho = rho_l - rho_g; mu_l = C_MU_L(cell, thread_l); /*compute slip*/ abs_v = sqrt(slip_x*slip_x + slip_y*slip_y + slip_z*slip_z); /*compute Reynold's number*/ reyp = rho_l*abs_v*diam2/mu_l; /*compute Eotvos number*/ Eo = g*delta_rho*diam2*diam2/surface_t; /*compute particle relaxtion time*/ taup = rho_g*diam2*diam2/18./mu_l; void_g = C_VOF(cell,thread_g); void_l = 1.-void_g; /*compute C_D */ C_D1 =24.*(1.+0.15*pow(reyp, 0.687))/reyp; C_D2 = 8./3.*Eo/(Eo+4.); if(C_D1 > C_D2) C_D = C_D1; else C_D = C_D2; /*compute drag and return drag coeff, k_g_s*/ fdrgs = C_D*reyp/24.0; k_g_s = void_g*void_l*rho_g*fdrgs/taup; return k_g_s; } |
4楼2015-05-14 09:30:52